Squirming Under the Glare of Directed Light

There you are, a simple worm simply slithering along, when a light
from above strikes part of your body. Suddenly, you start wriggling in a new direction
– not one of your choosing. What has happened to your free will?

This sequence of images shows
that, when researchers shine light onto the head of a worm expressing photosensitive
proteins in its cells, the worm crawls in a triangular pattern. Courtesy of Hang
Lu, Georgia Institute of Technology.
In the lab of Hang Lu, an associate professor in the Georgia Institute
of Technology School of Chemical & Biomolecular Engineering in Atlanta, members
of the worm species Caenorhabditis elegans are wondering just that – or would
be if their brains were much, much larger. Their movement is being controlled by
light originating from a common LCD projector.Using light to control motion in lab animals is not new. The burgeoning
field of optogenetics has several success stories of rats and other creatures having
their neurons and muscle cells switched on and off by light. In every case, however,
the light has been delivered via a fiber optic placed in the brain or by illuminating
the animal’s entire body at once.

Lu and her colleagues, on the other hand, use an externally mounted
LCD projector to deliver small swaths of light to precise areas on the body of the
very tiny worm. As with animals in other optogenetic experiments, Lu’s worms
have been genetically engineered to have photosensitive proteins as part of their
sensory system. When blue, red or green light from the projector shines upon them,
some neurons and muscles are activated while others are switched off, propelling
the worms in any direction the researchers desire.

Lu’s team reported in the Jan. 9, 2011, online edition of
Nature Methods that scanning the light along the worms’ bodies from head to
tail caused backward movement when neurons near the head were activated and forward
when neurons at the opposite end were stimulated. The investigators also found that
the intensity of the light could affect the worms’ behavior.

Perhaps the next blockbuster science-fiction film could be about
aliens who change our DNA so that we can be manipulated by lights emitted from their
spacecraft. Or has that already been done?